The present invention relates to a method for modifying the physical properties of bituminous materials and to asphalt compositions obtained therefrom. More particularly, the present invention relates to a method of producing industrial asphalts. Industrial asphalts have many uses but are particularly useful in roofing applications.
The physical properties of asphalt vary over a wide range. FIG. 1 is a softening point-penetration plot for various industrial asphalt grades. The four rectangles in FIG. 1 outline the properties of Types I-IV industrial asphalts as defined by the American Society for Testing and Materials (ASTM-D312). The plot illustrates the tremendously varying properties required of industrial asphalts for different applications. Industrial asphalts have softening points above 135.degree. F.
The residue remaining from crude oil after distilling off the various cuts is known as asphalt, or is known as asphalt flux, or simply flux when it is used to make asphalt. Flux is treated in various ways to obtain industrial asphalts having a variety of uses.
The properties of bituminous materials may be modified by such well-known treating means such as solvent extraction, air-blowing and the like. One type of treatment involves air-blowing, with or without a catalyst and with or without a hydrocarbon diluent.
Air-blowing processes using phosphoric acid and other catalysts are known in the art for making industrial asphalts. However, air-blowing processes require complex and expensive air-blowing equipment which must meet ever more stringent air pollution regulations. Furthermore, air-blowing requires long processing times on the order of many hours. Similar products can sometimes be obtained by stirring asphalt at high temperature in the presence of a catalyst. One known catalyst is essentially pure phosphoric acid generally manufactured by the furnace process.
There are two types of phosphoric acid. The first, is pure, water-white phosphoric acid made by reacting P.sub.4 O.sub.10 with water in what is generally called the furnace process. This white phosphoric acid is available in concentrations ranging from very dilute up to about 116 percent. The second is called green phosphoric acid and is the crude phosphoric acid present after precipitation of sulfate by addition of a suitable ion (e.g., Ca++) to the sulfuric acid solution of the mineral phosphate. It is not only colored, but contains a few percent of impurities, chiefly dissolved salts. Green phosphoric acid is available in concentrations up to about 94 percent and is made by the wet process.
U.S. Pat. No. 3,751,278 discloses a process for treating asphalts without air-blowing using phosphoric acids having an H.sub.3 PO.sub.4 equivalent of greater than 100 percent. The compositions produced by this process are directed to paving asphalts particularly useful in highway construction and maintenance. Paving asphalts usually have softening points below 135.degree. F. and penetrations from 20 to 300 dmm at 77.degree. F. This patented process is particularly directed to treating asphalts to substantially increase the viscosity without a significant decrease in penetration.
U.S. Pat. No. 2,179,208 teaches a process for making asphalt which comprises air-blowing in the absence of any catalyst at a temperature of 300.degree. to 500.degree. F. for 1 to 30 hours followed by a second step of heating that material to a temperature greater than 300.degree. F. with a small amount of polymerizing catalysts. The catalysts include phosphoric acid, ferric chloride, BF.sub.3, etc. Using small amounts of these catalysts, products with melting points of 140.degree. F. or less were produced. The patent teaches that overall processing times are significantly reduced using this two-step process.
U.S. Pat. No. 2,762,755 teaches a two-step process for producing asphalt which comprises the steps of: (1) treating asphalt with from 1/10 to 10 percent phosphoric acid at a temperature from about 200.degree. F. to about 350.degree. F. for a period of time from 4 hours to 1/2 hour followed by the second step (2) of oxidizing the product of step (1) at a temperature from about 350.degree. F. to about 450.degree. F. to obtain the desired characteristics for the product asphalt.
U.S. Pat. Nos. 2,676,910 and 2,845,359 teach the use of P.sub.2 O.sub.5 with the exclusion of air in a process to modify asphalts. These patents are particularly directed at producing asphalts for canal linings or cutback asphalts.
U.S. Pat. No. 1,092,448 teaches a method of treating mineral oil with phosphoric acid at a temperature of approximately 300.degree. C. (572.degree. F.) to produce purified oils.
One object of the present invention is to produce an industrial asphalt in a simple one step process without any prior air-blowing treatment of the bituminous material feed stock or any post air-blowing treatment of the asphalt formed.
A second object of the present invention is to provide a process for producing industrial asphalts where treatment times are very short when compared to conventional air-blowing processes.
Another object of the present invention is to provide a process which can utilize as a feed, bituminous material which heretofore could not be used in making industrial asphalts by the prior art air-blowing process without the addition of substantial amounts of lower boiling hydrocarbons.
Another object of the present invention is to produce an industrial asphalt from green phosphoric acid that is not producible from white phosphoric acid.
Another object of the present invention is to produce an industrial asphalts having low viscosities.
Another object of the present invention is to produce an asphalt shingles containing high levels of fillers.
Other objects will be readily apparent to those skilled in the art from a reading of this specification.